*** WAV (RIFF audio files) Resource Interchange File Format *** Document revision: 1.1 *** Last updated: March 11, 2004 *** Compiler/Editor: Peter Schepers *** Contributors/sources: Various net documents The WAV file is a variant of the RIFF format, specifically used for audio. RIFF is a generic format used mainly for video (AVI) and audio. It is built up with "chunks" which contain a chunk ID and a chunk size. Below is a dump of a sample WAV file showing the header. 00 01 02 03 04 05 06 07 08 09 0A 0B 0C 0D 0E 0F ASCII ----------------------------------------------- ---------------- 0000: 52 49 46 46 D4 45 CC 01 57 41 56 45 66 6D 74 20 RIFFÔEÌúWAVEfmtú 0010: 10 00 00 00 01 00 02 00 44 AC 00 00 10 B1 02 00 úúúúúúúúD¬úúú±úú 0020: 04 00 10 00 64 61 74 61 B0 45 CC 01 95 00 6D FF úúúúdata°EÌú•úmú 0030: 97 00 77 FF 6E 00 25 FF 58 00 14 FF 75 00 ED FE —úwúnú%úXúúúuúíþ 0040: 62 00 33 FE 2C 00 07 FE C4 FF 7A FE 53 FF C3 FE bú3þ,úúþÄúzþSúÃþ 0050: 91 FF 83 FE 21 00 91 FE EB 00 0D FF FF 00 57 FF ‘úƒþ!ú‘þëúúúúúWú 0060: 98 00 C4 FF 9F 00 79 00 60 00 DD 00 07 00 1D 01 ˜úÄúŸúyú`úÝúúúúú $0000-0003: Chunk ID "RIFF" in ASCII ("RIFX" files identify the samples audio data in hi/lo format instead of the normal lo/hi format) 0004-0007: Chunk size (lo/hi) $01CC45D4=30,164,452 is the total size minus 8 (these first 8 bytes are not included in the overall size) 0008-000B: Chunk format "WAVE". This format requires two subchunks to exist, "fmt " and "data". 000C-000F: Subchunk1 ID "fmt ". This describes the format of the next DATA subchunk. 0010-0013: Subchunk size (lo/hi) $00000010 (usually this value for PCM audio) 0014-0015: Audio format (1=PCM, 2 and higher are custom) ($0001) - $0001 = standard PCM - $0101 = IBM mu-law (custom) - $0102 = IBM a-law (custom) - $0103 = IBM AVC ADPCM (custom) 0016-0017: Number of channels (1=mono, 2=stereo, etc) ($0002) 0018-001B: Sample rate per second (lo/hi) $0000AC44 = 44100 001C-001F: Byte rate per second (=sample rate * number of channels * (bits per channel/8)) $0002B110 = 176400 0020-0021: Block Align (=number of channels * bits per sample/8) ($0004). 0022-0023: Bits per sample (8=8 bits, 16=16 bits) ($0010). Samples not using the entire bit range allocated should set the unused bits off. 0024-0027: Subchunk2 ID "data". This chunk contains the audio samples. There can be more than one in a WAV file. 0028-002B: Subchunk2 size (lo/hi) ($01CC45B0=30,164,400) 002C-xxxx: Audio data (lo/hi), stored as 2's complimented signed integers in the following order: Sample 1: Channel1 (left) ($0095=+149) Sample 1: Channel2 (right) ($FF6D=-) Sample 2: Channel1 (left) ($0097=+151) Sample 2: Channel2 (right) ($FF77=-) Sample 3: Channel1 (left) ($006E=+110) Sample 3: Channel2 (right) ($FF25=-) Notes: 8-bit samples are stored as unsigned chars, with values ranging ranging from 0-255. 16-bit samples are stored as signed integers, with values ranging from -32768 to 32767 00 01 02 03 04 05 06 07 08 09 0A 0B 0C 0D 0E 0F ASCII ----------------------------------------------- ---------------- 2D402C: 4C 49 53 54 40 00 00 00 49 4E 46 4F 49 53 46 54 LIST@úúúINFOISFT 2D403C: 15 00 00 00 53 6F 6E 79 20 53 6F 75 6E 64 20 46 úúúúSonyúSoundúF 2D404C: 6F 72 67 65 20 37 2E 30 00 00 49 45 4E 47 02 00 orgeú7.0úúIENGúú 2D405C: 00 00 20 00 49 43 52 44 0B 00 00 00 32 30 30 33 úúúúICRDúúúú2003 2D406C: 2D 31 30 2D 31 37 00 02 .. .. .. .. .. .. .. .. -10-17úú........ Above is a dump of the end of a WAV file, with the LIST information chunk shown. The four bytes (40 00 00 00) immediately following the "LIST" identifier show the size of the LIST chunk, in LO/HI format. In this case, the chunk size is $00000040, or 64 bytes. 00 01 02 03 04 05 06 07 08 09 0A 0B 0C 0D 0E 0F ASCII ----------------------------------------------- ---------------- 02F488AC: 63 75 65 20 C4 00 00 00 08 00 00 00 01 00 00 00 cueúÄúúúúúúúúúúú 02F488BC: 00 C0 21 00 64 61 74 61 00 00 00 00 00 00 00 00 úÀ!údataúúúúúúúú 02F488CC: 00 C0 21 00 02 00 00 00 00 40 11 00 64 61 74 61 úÀ!úúúúúú@úúdata 02F488DC: 00 00 00 00 00 00 00 00 00 40 11 00 03 00 00 00 úúúúúúúúú@úúúúúú 02F488EC: 00 00 3A 00 64 61 74 61 00 00 00 00 00 00 00 00 úú:údataúúúúúúúú 02F488FC: 00 00 3A 00 04 00 00 00 00 00 59 00 64 61 74 61 úú:úúúúúúúYúdata 02F4890C: 00 00 00 00 00 00 00 00 00 00 59 00 05 00 00 00 úúúúúúúúúúYúúúúú 02F4891C: 00 C0 6C 00 64 61 74 61 00 00 00 00 00 00 00 00 úÀlúdataúúúúúúúú 02F4892C: 00 C0 6C 00 06 00 00 00 00 40 84 00 64 61 74 61 úÀlúúúúúú@„údata 02F4893C: 00 00 00 00 00 00 00 00 00 40 84 00 07 00 00 00 úúúúúúúúú@„úúúúú 02F4894C: 00 80 9A 00 64 61 74 61 00 00 00 00 00 00 00 00 ú€šúdataúúúúúúúú 02F4895C: 00 80 9A 00 08 00 00 00 00 00 AC 00 64 61 74 61 ú€šúúúúúúú¬údata 02F4896C: 00 00 00 00 00 00 00 00 00 00 AC 00 4C 49 53 54 úúúúúúúúúú¬úLIST 02F4897C: 84 00 00 00 61 64 74 6C 6C 61 62 6C 07 00 00 00 „úúúadtllablúúúú 02F4898C: 01 00 00 00 30 31 00 00 6C 61 62 6C 07 00 00 00 úúúú01úúlablúúúú 02F4899C: 02 00 00 00 30 32 00 00 6C 61 62 6C 07 00 00 00 úúúú02úúlablúúúú 02F489AC: 03 00 00 00 30 33 00 00 6C 61 62 6C 07 00 00 00 úúúú03úúlablúúúú 02F489BC: 04 00 00 00 30 34 00 00 6C 61 62 6C 07 00 00 00 úúúú04úúlablúúúú 02F489CC: 05 00 00 00 30 35 00 00 6C 61 62 6C 07 00 00 00 úúúú05úúlablúúúú 02F489DC: 06 00 00 00 30 36 00 00 6C 61 62 6C 07 00 00 00 úúúú06úúlablúúúú 02F489EC: 07 00 00 00 30 37 00 00 6C 61 62 6C 07 00 00 00 úúúú07úúlablúúúú 02F489FC: 08 00 00 00 30 38 00 00 .. .. .. .. .. .. .. .. úúúú08úú........ Above is the "cue " chunk layout, also at the end of the WAV. These describe cue points (or markers) placed in the WAV file. To analyse a WAV file quickly is very easy: 1. Examine the initial chunk ID (RIFF) and its size. The size should be the filesize-8. 2. Check for the WAVE chunk ID next. If it's not there then you don't have a proper WAV file. 3. Now you can start checking the individual sub-chunks. Read in 8 bytes. The first four are the sub-chunk ID and the last four are the sub-chunk size. If you want to check the contents of the sub-chunk thats up to you. 4. If you seek forward in the file the size of the sub-chunk you will find yourself at the next sub-chunk. WAV files can also have other sub-chunk ID's such as FACT, ASFP and LIST. I will not get into the specifics of these. There are other more extensive documents on the web that describe the WAV and RIFF format much better than I can.